Generally, light source systems using light emitting diode (LED) chips are constructed by mounting LED chips in various kinds of packages according to desired uses of the systems. A side-view LED package is disposed at a lateral side of a light guiding plate to provide light in parallel to the light guiding plate. Thus, the side-view LED package is mainly used for backlight illumination for a variety of displays.
FIGS. 1 and 2 are a plan view and a perspective view illustrating a conventional side-view LED package, respectively, and FIG. 3 is a sectional view taken along line A-A in FIG. 1.
Referring to FIGS. 1 to 3, the side-view LED package includes a pair of lead terminals, i.e., first and second lead terminals 11 and 13. The first and second lead terminals are formed from a lead frame, which is made of a phosphor bronze plate, and have surfaces plated with silver (Ag) to improve their reflectivity. The first and second lead terminals 11 and 13 are supported by a package body 15. The package body 15 is formed by insert-molding the lead terminals with polyphthalamide (PPA).
For the sake of convenience of description, the package body 15 can be divided into an upper package body 15a and a lower package body 15b with respect to the position of the first and second lead terminals 11 and 13.
The upper package body 15a has a cavity 16 through which the first and second lead terminals 11 and 13 are exposed. The first and second lead terminals 11 and 13 are positioned at a bottom of the cavity 16, i.e., on the lower package body 15b, and are spaced apart from each other within the cavity. Further, the first and second lead terminals 11 and 13 protrude outside of the package body 15 so as to be electrically connected to an external power source. The outwardly protruding first and second lead terminals 11 and 13 may have a variety of shapes and may be bent in different forms. FIGS. 1 and 2 show the lead terminals 11 and 13 that are bent laterally at a lower surface of the package body 15 so as to ensure surface mounting.
An LED chip 17 is mounted on and electrically connected to the first lead terminal 11 within the cavity 16, and is then electrically connected to the second lead terminal 13 by means of a bonding wire. The cavity 16 may be filled with a light-transmitting resin 23 and phosphors may be contained in the resin.
In the conventional side-view LED package, the cavity 16 is formed to be elongated, and sidewalls defining the cavity, particularly sidewalls 15w on a major axis direction are formed to be inclined so that a viewing angle is increased in the major axis direction. Accordingly, it is possible to provide a side-view LED package suitable for a backlight of a display, and further to provide a side-view LED package capable of emitting white light depending on a proper selection of an LED chip and a phosphor.
However, the conventional side-view LED package has a problem in that light emitted from an LED chip toward the inner walls 15w is absorbed and scattered by the inner walls 15w of the package body, which have low reflectivity, resulting in deterioration of optical efficiency. Further, the inner walls of the package body made of PPA material are discolored by the light incident directly on the package body 15 from the LED chip. Thus, as the LED package is used for a long time, the optical efficiency is further deteriorated, resulting in a decrease in the lifespan of the LED package.
Moreover, since the package body 15 made of a material such as PPA has poor heat-dissipating performance, heat generated in the LED chip cannot be easily dissipated to the outside. As a result, junction temperature increases in the LED chip during operation of the LED chip, leading to deterioration of the optical efficiency.
Meanwhile, if the cavity 16 is filled with the light-transmitting resin 23 containing phosphors, an upper surface of the light-transmitting resin 23 is in the form of a meniscus, resulting in deterioration of the optical efficiency. If the amount of the light-transmitting resin 23 is increased to solve this problem, the light-transmitting resin 23 protrudes upwardly beyond an upper surface of the package body 15 and thus may be easily damaged by an external force. Accordingly, there have been conducted studies on a method of forming a wavelength-converting member confined within the cavity 16 by dotting a small amount of liquid resin containing phosphors on the LED chip. However, since the liquid resin flows down due to the flat bottom of the cavity 16, it is difficult to form a convex wavelength-converting member.